Videobrain arrives

Been wanting one of these for eons... finally got one at a not crazy price.







Pretty much what I thought it would be, which is rare -- usually these things end up being bigger or much smaller than the pictures suggest and work way differently than what I expect. The keyboard is almost comparable to a modern USB keyboard in terms of feel -- definitely better than the Commodore 64 I grew up with, although the lack of a separate Return key is a bit.. odd.

The cartridge mechanism needs some work.. doesn't want to lock down. The cartridges are bizarre.. it's sort of like a Nintendo where you push it down. But they're huge for what they are!

The joysticks do not seem to self-center. I'm not sure if that's a feature or if they've just worn out. I can't get Blackjack to respond to their movements (you're supposed to use them to place bets, etc), but the fire buttons work.

Strange little machine. Together with the Interact Model One and the Bally Computer, I'd say we have an 'unholy' trinity to balance the PET, TRS-80 and Apple II.

More pics. I'm curious what hooked up to the accessory port.

falter said:

More pics. I'm curious what hooked up to the accessory port.

View attachment 32917 View attachment 32918

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Stuff like the Expander 1 and 2. I have a page on the Videobrain here: http://www.atariprotos.com/othersystems/videobrain/videobrain.htm

Thanks!! That's a great site!

Looks like the odds of ever seeing a Videobrain expander in the wild are slim to none, likewise with the programming cartridge.

Are you able to tell me if the joysticks are supposed to be self centering?

The video looks impressive for 1977. I wonder what the video hardware looks like.

You think USB keyboards have a better feel than a C64?

Yeah the video is not bad -- it's very similar to the Interact Model One I have.

I'll take some pics inside when I get around to fixing the cartridge door mechanism.

I'm a loyal C64 guy but even back in the day I *hated* the feel of the keyboard. I like keyboards with a sort of laptop-keyboard feel.. that's what this feels like.

No the joysticks are not self centering.

Decided to go in and fix the cartridge door, so I took some interior pics.





It's quite a job getting into this thing. The design is fairly elegant, and there's not too many screws but the wires present a bit of a challenge getting around. The power supply (?) just sits in a couple of plastic slots. The motherboard seems fairly well organized.

I also opened up the joysticks to see what was up in there. The computer is registering the fire button but not the movement of the joystick itself.



I tested the little (potentiometers?) dials that move when the joystick stick is moved... they appear to be adjusting resistance just fine. So I'm not sure where my problem is. I'm hoping it's not back inside the machine.. would really hate to have to go in there again!

The problem is certainly inside the unit, if both controllers are "bad".

Check the voltage at those pots before you tear it all apart.

Those sockets look look like the kind Commodore used. I don't trust them.

Check the power supply voltages, if you can.

I found the schematic: http://www.seanriddle.com/vb/videobrain4.jpg

And looking at my photos again, it looks kinda like U17 has been messed around with. The machine isn't apart right now but the solder around the chip legs was messy relative to everything around. And someone had clearly been in the machine before. Heh. Another project!

The pot measurement works by charging a capacitor and then measuring
how long it takes to discharge.
In the instructions, it said it was suppose to have an auto center function
but I never got it to do anything. It always had a bias one way.
I never though of going inside the joystick to correct it.
It likes to use 100K pots as I recall. If you choose to use other joysticks,
it is good to know that most project joy sticks are 10K.
I believe it is just mechanically moving the pots.
As for being constantly firing, I'd make sure the circuit is
doing the make and break of the switch.
As for the other fellow's question about the video chip, there is another
fellow that has recreated the video chip from patent information and testing
in an FPGA.
He did publish a document on how the registers work.
The memory system is a little funny. There are two places where
memory is. One is on video timing while the other is on processor
timing. There is an arbitrator there for when the processor wants
to access the video but I don't recall how it works.
Dwight